A crankcase for a multiple-cylinder four-cycle engine, including an upper crankcase and a lower crankcase which are joined to each other at a joint surface; a separating wall which is integrally cast with the upper crankcase and the lower crankcase to extend from the joint surface toward the opposite side of the joint surface and are configured to define crank chambers corresponding to adjacent cylinders; and a crank journal bearing hole which is formed on the separating wall and is configured to support a crankshaft. At least the separating wall formed in the upper crankcase has a thickness that increases from the joint surface of the crankcase to a region near a deepest portion of the crank journal bearing hole and decreases from the region near the deepest portion of the crank journal bearing hole toward the opposite side of the joint surface of the crankcase.